DE2915222B2 - Device for continuous alternating current supply to consumers - Google Patents

Description

35

40

45 contains lais, by means of which during the discharge of the battery to test the capacity when a minimum discharge voltage is reached or after a specified discharge time and / or be! a power failure or another disturbance influencing the capacity test, the capacity test is ended and, when the AC network is intact, the switchover to battery charging can be controlled automatically via the static converter acting as a rectifier

6. Control device according to claim 5, characterized in that after the expiration of a a predetermined time for the verification of sufficient battery capacity a message signal is generated and the capacitance test continues to run automatically until it is monitored by the discharge voltage is ended, whereupon the total discharge time is displayed, and that after the end of the Capacity test is automatically switched to battery charging.

7. Control device according to claim 5, characterized in that through it in the event of a power failure the capacity test is interrupted and the consumers respond to the as Inverter acting static converters are switched and that when the Voltage of the alternating current network the consumers are switched back to the alternating current network and then either the capacity test is continued or automatically when the battery is charged is switched.

8. Control device according to claim 1 to 5, characterized in that by it at the Discharge the battery to the capacity test a fixed phase deviation for a desired one Active current is set, and changes in the mains voltage are thereby caused by feedforward interference be balanced.

9. Device according to claim 1 to 4, characterized in that the impedance with an inductance L is dimensioned so that with a given line voltage and set phase deviation of the AC voltage of the static converter from the line voltage, a desired current flows at a given power factor (cos φ).

The invention relates to a device for the continuous alternating current supply of consumers with normal power supply from an alternating current network or via one controlled as an inverter static converter, in which device a first switch between the AC network and the Consumers (on the one hand) and a second switch between the consumers and the inverter (on the other hand) are arranged.

Such a device is known from DE-AS 03 221 as an arrangement for uninterrupted t, 5 Power supply of an alternating current consumer. There is one with the mentioned first switch functionally comparable switching element designed as a switching contact of a voltage-sensitive relay, which is closed when the voltage of the AC network used is sufficiently high. This is when the switching contact is closed to the output transformer of an inverter controlled reversible converter connected via a choke and thus to the AC output of the Converter coupled, with a phase difference between the line voltage and the inverter voltage consists. This is recorded by means of a control unit assigned to the static converter, which is switched on or off depending on the mains voltage by the voltage-sensitive relay will. The phase difference is controllable and results

a control of the current and charge flow of the static converter either from the battery to the Consumer or from the AC mains into the battery. The mentioned choke is part of a saturated resonance circuit, which is assigned to the output transformer of the converter, see above that the output transformer is like a constant voltage transformer Acts when the AC grid fails and the static converter acts as an inverter takes full power for the consumer, then ι ο the choke limits this current.

The facility in question can only work with a specifically trained inverter and it is as the output transformer acts as a voltage stabilizer is designed, only suitable for the delivery of small services

From DE-AS 24 52 921 a device of the type mentioned is also known which represents a circuit arrangement for the interruption-free power supply of AC consumers This contains a reversible static converter, controlled as an inverter for the Backup power supply of consumers with alternating current, if the normal power supply from a AC grid has failed With normal power supply, the load is from the AC grid the mentioned converter ge as a rectifier? expensive for charging or recharging a battery, which is used as an energy source is used for the backup power supply. The AC output (see Fig. 3) of the reversible statistic Converter is connected directly to the consumer and is in an intact AC network connected to the grid without additional impedances. This results in a complex device. Above this is the harmonic distortion of the mains current when the battery is charged, and it will be if the Converter no longer supplies the consumers with voltage

Furthermore, a device of the type specified is known from DE-AS 20 14 680 likewise a circuit arrangement for the uninterrupted AC power supply to a consumer represents, with a reversible static converter for the alternating current supply of the consumer, without filter element or choke at the alternating current output, or for charging a battery, which is used as a The energy source in the AC power supply of the consumer is used between the AC output of the converter and the consumer on the one hand and an alternating current network on the other hand is such a thing electronically controlled static switch located directly at the AC output of the converter a current transformer for recording the converter alternating current is connected. It is the converter a so-called reactive current circuit and an active current circuit are assigned; the outcome of the former has an effect a voltage regulator, the output of the latter as well as the voltage of the battery act through one Voltage comparator on a frequency regulator.

These two control systems, which are meshed with one another, have the effect that the existing Mains voltage the electronic switch is closed, and when the battery voltage is sufficiently large and the converter is controlled as an inverter, the inverter voltage to the grid voltage is adapted and is synchronized with this. If, on the other hand, the battery spam has dropped, the Battery charged via the converter controlled as a rectifier. If the Netzspanming falls off, then the electronic switch is opened and it becomes the Converter for backup power supply controlled as an inverter

It is also this facility for running it here The functions provided are relatively expensive, especially since there are several control variables when the functions are executed influence each other, since the mentioned control systems are not decoupled from each other.

The object on which the invention is based is an improvement and training for Multipurpose use of the device defined at the outset in such a way that it is thus using In comparison with the state of the art considered above, few circuit and electronic means are one energy-saving continuous alternating current supply is made possible, in which particular discharge periods should be included for the capacity test of the battery.

This object is achieved by the features characterized in claim 1 an impedance and a third switch between the static converter and the AC network arranged and it is assigned to the static converter an additional control device with the in each case by setting a phase deviation between the AC voltage of the converter and the voltage of the alternating current network, synchronization of these alternating voltages for parallel operation of the inverter and the AC network is effected and with normal power supply of the consumer for the battery is charged from the alternating current network via the converter acting as a rectifier flowing current or from the battery via the converter acting as an inverter into the alternating current network flowing current for discharging the battery is adjustable or controllable

According to one embodiment of the invention according to claim 2, the first and the second switch can be bridged by a connection between the alternating current network and the static converter via a choke as an impedance by means of a third switch
or a choke is arranged as an impedance between the first switch and the consumers and a bypass switch is assigned to this choke (claim 3)

or it is just the second switch through a connection between the AC mains and the static converter can be bridged via a choke as impedance by means of a third switch.

Furthermore, according to the invention, the aforementioned choke is dimensioned so that for a given mains voltage and The set phase deviation of the inverter voltage from the grid voltage is a desired one Current flows at a given power factor (cos φ)

With the device designed according to the invention, the aforementioned throttle is used in every operating mode the continuous alternating current supply, also with the operating modes charging and discharging the battery, in In contrast to the known devices considered above, a reliable decoupling of the converter and the alternating current network. The charging current (for the battery) can be regulated with the phase deviation between the output voltage of the converter acting as a rectifier (for the battery) and the Mains voltage. Furthermore, with the phase deviation between the output voltage of the inverter acting converter and the mains voltage of the

Discharge current of the battery, during the capacity test, adjustable or adjustable.

If the mains voltage is available, the normal current supply of the consumers is also possible if (only) the switch assigned to the output of the converter is closed. Then the consumer voltage becomes practical if the choke is dimensioned appropriately not influenced by fluctuations in the mains voltage. If the converter fails, the consumers can be switched directly to the alternating current network, ι ο

A device according to the invention can finally be adapted to an available corresponding AC network with a single-phase or a three- or multi-phase static converter for Battery charging or equipped for capacity testing.

The invention is described below with reference to the drawing through exemplary embodiments in which

F i g. 1 is a block diagram of the device according to the invention,

F i g. 2 is a block diagram of the device with a different arrangement according to the invention;

F i g. 3 to explain the control processes in a device according to the invention according to FIG. 1 or 2 a Shows the vector diagram of the battery charging mode,

4 shows a phasor diagram of the capacity test operating mode to explain the control processes represents

For a description of a first exemplary embodiment, reference is made to FIGS. 1 referred to. The device shown as a block diagram is connected to two energy sources, an alternating current network Af on the one hand and a storage battery B. The device contains a static single-phase converter, a thyristor converter, which is hereinafter referred to as converter WR for short. In addition to a control unit with which the control pulses for the thyristors of the converter are generated and fed to the thyristors, an additional control device is assigned to the converter; by means of the additional control device, the phase position of the converter voltage uwr can be changed to the mains voltage by synchronous converter voltage. The (reversible) converter, viewed as a quadrupole, has two pairs of poles, a direct current and an alternating current pole pair, each of which can be an input or an output depending on its mode of action. Hereinafter, both, however, referred to as outputs to the DC output of the converter is connected to the battery B and to the AC output at the AC mains M. Of the two phase conductors, through which the transducer is connected to the AC mains, branches off a consumer leaving to consumers V ab. A first (S 1) and a second switch (S2) are located in one of the two phase conductors. Si is connected on the one hand to the alternating current network and on the other hand to the consumers and the converter; S2 is connected on the one hand to the consumers and the AC network and on the other hand to the converter. Either S1 or S2 is closed. An impedance, according to FIG. 1 and 2 a throttle D, which according to F i g. 1 Sl and S 2 bridging current branch with a third switch S3 between M and the system (B, WR) is arranged in a row, the switch, serves as decoupling element other hand, in a second embodiment (according to Figure 2) the restriction D in a phase conductor between S1 and the consumer outlet. Here the throttle is a bypass switch SA assigned. In a third exemplary embodiment (not shown), the throttle D is connected to a third switch S3 in a connection between WR and M that bridges only the first switch S1.

The device described is intended for a continuous alternating current supply of consumers, in which basically two systems, a static inverter with a battery and an alternating current network work together, mostly in parallel operation of the inverter and the alternating current network via the choke D, furthermore for the power supply of consumers alone from the battery-inverter system, namely backup power supply, if the AC network used for normal current supply of consumers has failed, and finally to normal current supply from network M, with S1 being closed and the inverter running synchronously with the network, the battery being charged via S3 and is kept in readiness for a power failure A continuous alternating current supply requires that the battery is kept in readiness for the backup power supply, and sufficient energy must be stored in the battery at all times. For this purpose, instead of an inverter, a reversible converter, as described above, is used, which can be controlled as a rectifier during normal current supply to charge the battery. In certain applications, a continuous power supply requires a device with which the storage capacity of the battery can be checked by capacity tests. A capacity test is carried out by discharging the battery and removing an amount of charge, & h. of a certain discharge current in a certain period of time With the aid of the device described above, a capacity test can be carried out in an energy-saving manner during normal current supply by discharging the battery into the network via the converter acting as an inverter. Other possible modes of operation are: Charging the battery or capacity test when the mains voltage is available, with S3 being closed and the loads being supplied from the inverter via the closed switch S 2.

A decoupling and a control function are intended for the above-mentioned throttle D in all of the above-mentioned operating modes. Without an impedance or throttle, there is a rigid coupling of the systems (M, WR and B) in parallel operation. Difficulties arise in the voltage regulation and synchronization regulation of the inverter, which can only be mastered with great effort by control means. In order to suppress equalizing currents between the two systems, the amplitudes of the alternating voltages and the phase angles must be regulated equal to each other. By an impedance between the systems, e.g. B. an inductance is a flexible coupling caused Dabe is produced by the control of the inverter and a control loop with controller for the phase angle or the frequency of the inverter synchronous operation with eini certain phase deviation Διρ between the AC voltages u _M and uwr , so that the inverter with mains frequency running At the dresse D there is an alternating voltage i / o with a phase position which is represented as a differential voltage u _D = u _M - u _m The current h flowing in the choke is ζ. Β in the operating modes battery charge or capacity ^ probe lagging by 90 ° el compared to the voltage Ud

The fact that the inverter WR and network M is decoupled by the throttle means that control loops that can be assigned separately to WR and M are safely separated from one another. The energy flow between the systems mentioned in> charging the battery from the mains via the acting as a rectifier converter WR or the acting as an inverter transformer in the capacity test is determined by the phase difference Δψ the voltage UWr of the mains voltage. In the first case (see Fig. F i g. 3) to face, leading UWr, it flows an active current from the network. In the second case (see Fig. F i g. 4) to face UWr lagging, an effective current flowing into the network. In this case, the inverter is loaded with an (inductive) current lagging behind by the phase angle φ r>, which discharges the battery.

The choke D minimizes the effects of interfering influences emanating from the alternating current network on the alternating current output of the converter or inverter.

When compared to UWr leading-supply voltage to the power i'm from the network to 1/2 x ΔΨ is lagging. If um and Uwr have the same amplitudes, the consumer outlet according to F i g applies in the node point. 1 with closed switches S 2 and 53 the relationship

IWR + 'M = IvOm = Id) -

When switches S1 and S2 are closed, the relationship is the same, with iwr = - io . At zero consumer current (i _v = 0), this results in a direction of energy flow that is directed from M via WR into battery B.

To illustrate the relationships between the voltages and currents that exist in the modes of operation considered above, the phasor diagrams in FIGS. 3 and 4 are shown in the complex numerical plane (Im = imaginary, Re = real) the inverter voltages have the same values and that there is no load

It can then be shown that the relationship

«O = 2 u

sin

Δ Ψ

There is an inductance L of the throttle D can be given on the basis of this relationship, with which the throttle fü. most uses as a decoupling and as a control for continuous

45

50 power supply is adequately designed and dimensioned. The choke has an inductance

L.

(Ul _n

U ₁₁ sin

Δ Ψ

where u _M = 220 volts, ω = 314 / s and υαΔΨ each mean fixed limit values. To determine L , values for the inductor current / O and for the phase deviation ΔΨ must be specified. This shows that the choke is optimally designed when a phase deviation of a maximum of approximately 60 ° el is selected. This avoids an undesirably high load on the inverter WR even in the event of a power failure or a short circuit, and the line current i'wr is also limited. In the design explained above , changes in the line voltage have only a slight effect on the inverter current.

The above-mentioned additional control device includes voltage relays, current relays and / or Timing relay further and special control functions for the operating modes discharging the battery Capacity test as well as charging the battery. There are these control functions that as soon as a predetermined so-called minimum discharge voltage is reached or after a predetermined one has expired Discharge time such as B. after 3 hours, and / or in the event of an AC power failure or a other disturbance influencing the capacity test, the discharging of the battery for the capacity test is ended or is interrupted and then the power supply device, whenever the AC network is intact, the battery charging mode is automatically switched to. As contains further control functions the control device that after a predetermined discharge time for the detection of a sufficient Battery capacity an identification signal is generated for this, but the capacity sample depends on the monitored discharge voltage of the battery is terminated, that then the discharge time is displayed and the Device is automatically switched to battery charging.

Furthermore, after the capacity test has been interrupted as a result of a power failure, the loads are quickly switched to system B, WR to the backup power supply.When the mains voltage returns, the loads are switched back to the AC network, then the capacity test is continued or it is switched to the battery charging mode

1 sheet of drawings

Claims (5)

Patent claims: 1. Device for the continuous alternating current supply of consumers from one AC mains or via a static converter acting as an inverter, in which Establishing a first switch between the AC network and the consumers (on the one hand) as well as a second switch is arranged between the consumers and ι ο the inverter (on the other hand), characterized in that between the static converter and the alternating current network an impedance and a third switch are arranged and that the static converter an additional control device is assigned, each by setting a Phase deviation of the alternating voltage of the converter from the voltage of the alternating current network a synchronization of these alternating voltages for the parallel operation of the inverter and the AC network is effected and with normal power supply of the consumer for the charge the battery is a flowing from the AC network via the converter acting as a rectifier Electricity or from the battery via the converter acting as an inverter into the alternating current network flowing current for discharging the battery is adjustable or controllable 2. Device according to claim 1, characterized in that the first and the second switch through a connection between the AC network and the static converter via a choke as Impedance can be bridged by means of a third switch. 3. Device according to claim 1, characterized in that between the first switch and the Consumers a choke arranged as an impedance and that the choke is a bypass switch assigned. 4. Device according to claim 1, characterized in that only the second switch by a Connection between the AC network and the static converter via a choke as Impedance can be bridged by means of a third switch 5. Control device according to claim 1 to 3, characterized in that the control device Voltage relays, current relays and / or timing devices 30th